Iran has slowed down the expansion of its nuclear enrichment programme at its plant in Natanz, UN nuclear chief Mohamed ElBaradei has said.

The IAEA secretary general also said he was sending a team of officials to Tehran on Tuesday for discussions.

Iran insists that its nuclear programme is for purely civilian purposes.

Tehran is under growing pressure from the US and EU to halt enrichment, and the UN has passed two resolutions and packages of sanctions against it.

So far Iran has been defiant, vowing repeatedly to install thousands of the centrifuges that, when run in a series, enrich uranium.

'Slow commissioning'

"We have seen a fairly slow development in commissioning new cascades," Mr ElBaradei said.

He said International Atomic Energy Agency inspectors had noticed Iran's slowdown "in commissioning new cascades for the treatment of nuclear material" while on a visit to the nuclear facility at Natanz last week.

Mr ElBaradei welcomed this.

"Iran needs to do everything to cool things down," he said. "[There is a] need to shift from the mode of confrontation to the mode of goodwill and co-operation."

Mr ElBaradei repeated a call for the United States to speak directly to Iran about Iran's nuclear programme.

"I think that would help for in many ways for us to make progress. You need to understand where each other is coming from," he said.